- Added `ColumnHeader`, `EmptyState`, and `DropZone` components to improve the Kanban UI structure and user experience.
- Refactored `KanbanColumn` to utilize the new components, enhancing readability and maintainability.
- Updated `Card` component to support flexible props for shadow, border, and background, allowing for better customization across the application.
- Adjusted `SwimlanesBase` to incorporate the new `ColumnHeader` for consistent column representation.
